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Improved nucleus pulposus implants are provided to better accommodate the
disc nucleus space, to provide a modified compressive modulus, to
facilitate positioning, to enhance fixation, and to facilitate effective
implantation and use. Some implants have sloped upper and/or lower
surfaces to provide a "wedge-shaped" implant, while other implants have
circumferential grooves, and/or have radiographic markers, and/or are
modified by including a material having a compression profile that
differs from the compression profile of the predominant material of the
implant. Some implants have surface features to enhance fixation to
surrounding surfaces.

1. An intervertebral disc nucleus pulposus implant, comprising a load
bearing elastic body sized for introduction into an intervertebral disk
space, said body having an anterior portion including an anterior side,
and a posterior portion including a posterior side, wherein at least half
of said posterior portion tapers to the posterior side of the implant.

2. An intervertebral disc nucleus implant according to claim 1 wherein the
entire posterior portion tapers to the posterior side of the implant.

3. An intervertebral disc nucleus implant according to claim 1 wherein at
least part of said anterior portion tapers to the posterior side of the
implant.

4. An intervertebral disc nucleus implant according to claim 1 wherein
substantially all of said anterior portion tapers to the posterior side
of the implant.

5. An intervertebral disc nucleus implant according to claim 1 wherein at
least part of said anterior portion tapers to the anterior side of the
implant, and at least part of said posterior portion tapers to the
posterior side of the implant.

6. An intervertebral disc nucleus implant according to claim 1 wherein
said implant further includes one or more radiographic markers in the
implant to facilitate positioning of the implant.

7. An intervertebral disc nucleus pulposus implant according to claim 1
wherein said implant further includes a flexible peripheral supporting
band disposed circumferentially about said elastic body for reducing
deformation of said body.

8. An intervertebral disc nucleus pulposus implant according to claim 1
wherein said implant further includes at least one surface feature to
enhance fixation of the implant to surrounding surfaces.

9. An intervertebral disc nucleus pulposus implant according to claim 8
wherein said surface feature comprises a three-dimensional porous surface
on the implant to enhance fixation of the implant to surrounding
surfaces.

10. An intervertebral disc nucleus pulposus implant according to claim 1
wherein said load bearing elastic body has one or more substantially
horizontal grooves along a side surface of the implant to reduce the
material in the side surface, thereby facilitating deformation of the
implant under load and allowing a greater range of motion.

11. An intervertebral disc nucleus implant according to claim 10 wherein
said grooves extend substantially completely around the circumference of
the implant.

12. An intervertebral disc nucleus pulposus implant according to claim 1
wherein said implant has one or more areas that have a compressive
modulus that is different from the compressive modulus of the predominant
load bearing portion of the implant, thereby providing an implant with
load bearing portions that are more or less stiff than other load bearing
portions of the implant.

13. An intervertebral disc nucleus implant according to claim 12 wherein
one or more areas of the implant is modified by including in that area a
polymeric material having a compressive modulus that is different from
the compressive modulus of the predominant load bearing portion of the
implant, thereby providing an implant with load bearing portions that are
more or less stiff than other load bearing portions of the implant.

14. An intervertebral disc nucleus implant according to claim 12 wherein
one or more areas of the implant is modified by including in that area a
hydrogel material having a compressive modulus that is different from the
compressive modulus of the predominant load bearing portion of the
implant, thereby providing an implant with load bearing portions that are
more or less stiff than other load bearing portions of the implant.

15. An intervertebral disc nucleus implant according to claim 12 wherein
one or more areas of the implant is modified by including in that area a
metalic material having a compressive modulus that is different from the
compressive modulus of the predominant load bearing portion of the
implant, thereby providing an implant with load bearing portions that are
more or less stiff than other load bearing portions of the implant.

16. An intervertebral disc nucleus implant according to claim 12 wherein
one or more areas of the implant is modified by including in that area a
ceramic material having a compressive modulus that is different from the
compressive modulus of the predominant load bearing portion of the
implant, thereby providing an implant with load bearing portions that are
more or less stiff than other load bearing portions of the implant.

17. An intervertebral disc nucleus pulposus implant according to claim 12
wherein said implant is modified by including one or more voids in the
implant to provide at least one load bearing portion having a compression
resistance that is different from the compression resistance of other
load bearing portions of the implant.

18. An intervertebral disc nucleus pulposus implant according to claim 1
wherein implant comprises a load bearing elastic body sized for placement
into an intervertebral disc space, said body having a first end, a second
end, a central portion, and a first configuration wherein said first end
and said second end are positioned adjacent to said central portion to
form at least one inner fold, said elastic body configurable into a
second, straightened configuration for insertion through an opening in an
intervertebral disc annulus fibrosis, said body configurable back into
said first configuration after said insertion.

19. An intervertebral disc nucleus implant according to claim 1 wherein
said load bearing elastic body is made of an elastomeric material or a
hydrogel.

20. An intervertebral disc nucleus implant according to claim 19 wherein
said elastomeric material is a silicone, polyurethane, polyolefin,
neoprene, nitrile, or vulcanized rubber, or a mixture of one or more of
said materials.

21. An intervertebral disc nucleus implant according to claim 19 wherein
said hydrogel is a natural hydrogel or a hydrogel formed from one of more
members of the group consisting of polyvinyl alcohols, acrylamide-based
hydrogels, polyurethanes, polyethylene glycol, poly(N-vinyl-2-pyrrolidone-
), acrylate-based hydrogels, N-vinyl lactams, and polyacrylonitriles.

22. An intervertebral disc nucleus implant according to claim 19 wherein
said load bearing elastic body is covered by an amount of biocompatible
material sufficient to substantially or completely cover the load bearing
elastic body.

24. A method of treating a medical patient, said method comprising
implanting in an intervertebral disc space of the patient an
intervertebral disc nucleus pulposus implant, wherein said intervertebral
disc implant comprises a load bearing elastic body sized for introduction
into an intervertebral disk space, said body having an anterior portion
including an anterior side, and a posterior portion including a posterior
side, wherein at least half of said posterior portion tapers to the
posterior side of the implant.

25. A method according to claim 24 wherein a stem cell material is
additionally added to the intervertebral disc space.

26. A method according to claim 24 wherein a collagen-rich tissue material
is additionally added to the intervertebral disc space.

27. A method according to claim 24 wherein a second agent is additionally
added to the intervertebral disc space; wherein said second agent is
selected from the group consisting of analgesics, antibiotics,
radiocontrast materials, growth factors, crosslinking agents,
polysaccharides, hormones, proteoglycans, and agents effective for
treating degenerative disc disease.

28. An intervertebral disc nucleus pulposus implant, comprising a load
bearing elastic body sized for introduction into an intervertebral disk
space, said body having one or more substantially horizontal grooves
along a side surface of the implant to reduce the material in the side
surface, thereby facilitating deformation of the implant under load and
allowing a greater range of motion.

29. An intervertebral disc nucleus pulposus implant, comprising a load
bearing elastic body sized for introduction into an intervertebral disk
space, wherein one or more areas in the implant have a compressive
modulus that is different from the compressive modulus of the predominant
load bearing portion of the implant, thereby providing an implant with
load bearing portions that are more or less stiff than other load bearing
portions of the implant.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 09/943,441, filed Aug. 30, 2001, which is a
continuation-in-part of U.S. patent application Ser. No. 09/650,525,
filed Aug. 30, 2000 and issued Sep. 16, 2003 as U.S. Pat. No. 6,620,196.
This application is also a continuation-in-part of U.S. patent
application Ser. No. 10/253,453, filed Sep. 24, 2002, which is a
divisional application claiming priority from U.S. patent application
Ser. No. 09/650,525, referenced above. This application is also a
continuation-in-part of U.S. patent application Ser. No. 10/717,687,
filed Nov. 20, 2003, which is a continuation-in-part of U.S. patent
application Ser. No. 09/943,441, referenced above, and of U.S. patent
application Ser. No. 10/459,630, which is also a continuation-in-part of
U.S. patent application Ser. No. 09/650,525, referenced above. All of
said priority applications are hereby incorporated herein by reference in
their entirety.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to nucleus pulposus implants and
methods for their implantation.

[0003] The intervertebral disc functions to stabilize the spine and to
distribute forces between vertebral bodies. A normal disc includes a
gelatinous nucleus pulposus, an annulus fibrosis and two vertebral end
plates. The nucleus pulposus is surrounded and confined by the annulus
fibrosis.

[0004] Intervertebral discs may be displaced or damaged due to trauma or
disease. Disruption of the annulus fibrosis may allow the nucleus
pulposus to protrude into the vertebral canal, a condition commonly
referred to as a herniated or ruptured disc. The extruded nucleus
pulposus may press on a spinal nerve, which may result in nerve damage,
pain, numbness, muscle weakness and paralysis. Intervertebral discs may
also deteriorate due to the normal aging process. As a disc dehydrates
and hardens, the disc space height will be reduced, leading to
instability of the spine, decreased mobility and pain.

[0005] One way to relieve the symptoms of these conditions is by surgical
removal of a portion or all of the intervertebral disc. The removal of
the damaged or unhealthy disc may allow the disc space to collapse, which
would lead to instability of the spine, abnormal joint mechanics, nerve
damage, as well as severe pain. Therefore, after removal of the disc,
adjacent vertebrae are typically fused to preserve the disc space.
Several devices exist to fill an intervertebral space following removal
of all or part of the intervertebral disc in order to prevent disc space
collapse and to promote fusion of adjacent vertebrae surrounding the disc
space. Even though a certain degree of success with these devices has
been achieved, full motion is typically never regained after such
vertebral fusions. Attempts to overcome these problems have led to the
development of disc replacements. Many of these devices are complicated,
bulky and made of a combination of metallic and elastomeric components.
Thus, such devices require invasive surgical procedures and typically
never fully return the full range of motion desired.

[0006] More recently, efforts have been directed to replacing the nucleus
pulposus of the disc with a similar gelatinous material, such as a
hydrogel. However, there exists a possibility of tearing or otherwise
damaging the hydrogel implant during implantation. Moreover, once
positioned in the disc space, many hydrogel implants may migrate in the
disc space and/or may be expelled from the disc space through an annular
defect, or other annular opening. A need therefore exists for more
durable implants, as well as implants that are resistant to migration
and/or expulsion through an opening in the annulus fibrosis. The present
invention addresses these needs.

SUMMARY OF THE INVENTION

[0007] Improved nucleus pulposus implants are provided to better
accommodate the disc nucleus space, to have an improved range of motion,
to modify the compressive modulus of the implant, to facilitate
positioning, to enhance fixation, and to facilitate effective
implantation and use. Accordingly, in one aspect of the invention,
nucleus pulposus implants are provided that have sloped upper and/or
lower surfaces to provide a "wedge-shaped" or "tapered" implant. In other
aspects of the invention nucleus pulposus implants are provided that have
circumferential grooves, and/or have radiographic markers, and/or are
modified by including a material having a compressive modulus that
differs from the compressive modulus of the predominant material of the
implant, and/or are modified to include surface features that enhance
fixation to surrounding surfaces.

[0008] One object of the present invention is to provide nucleus pulposus
implants that better accommodate the disc nucleus space, that have an
improved range of motion, that have a modified or variable compression
profile, that facilitate positioning, and that facilitate effective
implantation and use.

[0009] These and other objects and advantages of the present invention
will be apparent from the description herein.

BRIEF DESCRIPTION OF THE FIGURES

[0010] FIG. 1 depicts a side view of a cross-section of a nucleus pulposus
implant, including an elastic body 15 surrounded by an anchoring outer
shell 30, implanted in the intervertebral disc space of a disc.

[0014] FIG. 5 shows a side view of a cross-section of a nucleus pulposus
implant, including an elastic body 15 surrounded by a supporting member
34, in the form of a band, wherein the supporting member is surrounded by
an anchoring outer shell 30, implanted in the intervertebral disc space
of a disc.

[0015] FIG. 6 depicts a side view of a cross-section of a nucleus pulposus
implant, including an elastic body 15 surrounded by a supporting member
37, in the form of a jacket, wherein the supporting member is surrounded
by an anchoring outer shell 30, implanted in the intervertebral disc
space of a disc.

[0016] FIGS. 7A-7D depict various patterns of a supporting member of the
present invention.

[0017] FIG. 8 depicts a side view of a cross-section of a nucleus pulposus
implant including an elastic body 15 surrounded by a supporting member
34, taking the form of a band, that is further reinforced, or otherwise
supported, by straps 420 and 430. The implant is surrounded by an
anchoring outer shell 30 and is shown implanted in the intervertebral
disc space of a disc.

[0019] FIG. 10 depicts a side view of an alternative embodiment of a
nucleus pulposus implant of the present invention that includes
peripheral supporting band 34" and securing straps 520, 530, 540 and 550
and is surrounded by an anchoring outer shell 30 and implanted in the
intervertebral disc space of a disc.

[0021] FIG. 12 depicts a top view of an alternative embodiment of a
nucleus pulposus implant having shape memory.

[0022] FIG. 13 shows a side view of the implant shown in FIG. 12.

[0023] FIGS. 14A-14J depict portions of nucleus pulposus implants with
surface modifications. FIGS. 14A-14H show side views of top portions of
the implants, and FIG. 14I and FIG. 14J show top views of the views shown
in 14C and 14D, respectively.

[0024] FIGS. 15A-15N show top views of alternative embodiments of nucleus
pulposus implants having shape memory in folded, relaxed configurations.

[0026] FIG. 17 depicts a top view of an alternative embodiment of a
nucleus pulposus implant of the present invention having a self-locking
feature. The implant is shown in its locked, relaxed configuration.

[0027] FIG. 18 depicts a side view of the implant of FIG. 17.

[0028] FIG. 19 depicts a side view of the implant of FIG. 18 in an
unfolded, non-locked, non-relaxed configuration.

[0034] FIG. 28 depicts a side cross-sectional view of one embodiment of a
spinal disc implant delivery tool configured to deliver the shape memory
implants described herein.

[0035] FIG. 29 depicts a view of another embodiment of a spinal disc
implant delivery device showing features of the tip portion.

[0036] FIGS. 30A-30J depict side views of surface features that may be
present on the surfaces of the tip portions of various spinal disc
implant delivery devices described herein.

[0037] FIG. 31 depicts a view of an alternative embodiment of a spinal
disc implant delivery device showing features of the tip portion.

[0038] FIG. 32 depicts how the spinal disc implant delivery device of FIG.
31 may be used to aid placement of a spinal disc implant.

[0039] FIG. 33 depicts a view of yet a further alternative embodiment of a
spinal disc implant delivery device.

[0040] FIG. 34 depicts a view of yet a further alternative embodiment of a
spinal disc implant delivery device showing features of the tip portion.

[0041] FIG. 35 shows a view of an alternative embodiment of a spinal disc
implant delivery device showing features of the tip portion.

[0042] FIG. 36 shows a side view of an alternative embodiment of a spinal
implant delivery device.

[0043] FIG. 37A depicts an end view of the device of FIG. 36, taken along
line 37A-37A.

[0044] FIGS. 37B-37F depict end views of tip portions of the disc implant
delivery devices described herein. The tip portions are of various shapes
and have variously numbered movable members.

[0045] FIG. 38 depicts a step in the method of implanting the shape memory
implants described herein into an intervertebral disc space.

[0046] FIG. 39-44 depict further steps in the method of FIG. 38.

[0047] FIG. 45-48 show top views of how selected spinal disc implant
delivery devices may be positioned in an intervertebral disc space for
delivery of a spinal implant.

[0048] FIG. 49 depicts an end view of the positioned spinal disc implant
delivery device of FIG. 45, taken along line 49-49.

[0049] FIGS. 50A-D show an embodiment of the present invention where the
implant has a substantially uniform height.

[0050] FIGS. 51A-D show an embodiment of the present invention where the
posterior portion of the implant has a height that decreases near the
posterior edge.

[0051] FIGS. 52A-D show an embodiment of the present invention where the
entire posterior portion of the implant has a height that decreases
toward the posterior edge.

[0052] FIGS. 53A-D show an embodiment of the present invention where the
heights of both the anterior and posterior portions decrease toward the
posterior edge.

[0053] FIGS. 54A-D show an embodiment of the present invention where the
implant has a height that decreases from the center toward both the
anterior and posterior edges.

[0054] FIGS. 55A-F show embodiments of the present invention that include
a circumferential groove.

[0055] FIG. 56 shows an embodiment of the present invention that is
modified by including one or more voids in the implant to modify the
compression modulus of the implant.

[0056] FIG. 57A-B show embodiments of the present invention that are
modified by including a compression modifier in the implant to modify the
compressive modulus of the implant.

[0057] FIG. 58 shows another embodiment of the present invention that is
modified by including a compression modifier in the implant to modify the
compressive modulus of the implant.

[0058] FIG. 59 shows an embodiment of the present invention that includes
radiographic markers in the implant.

[0059] FIG. 60 shows another embodiment of the present invention that
includes radiographic markers in the implant.

[0060] FIG. 61 shows an embodiment of the present invention that includes
a three-dimensional surface layer to enhance fixation of the implant to
surrounding surfaces.

[0061] FIG. 62 shows another embodiment of the present invention that
includes a three-dimensional surface layer to enhance fixation of the
implant to surrounding surfaces.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] For the purposes of promoting an understanding of the principles of
the invention, reference will now be made to preferred embodiments and
specific language will be used to describe the same. It will nevertheless
be understood that no limitation of the scope of the invention is thereby
intended, such alterations and further modifications of the invention,
and such further applications of the principles of the invention as
illustrated herein, being contemplated as would normally occur to one
skilled in the art to which the invention relates.

[0063] The present invention provides prosthetic intervertebral disc
nucleus pulposus implants that may fully or partially replace the
natural, or native, nucleus pulposus in mammals, including humans and
other animals. In one aspect of the invention, implants are provided that
are configured to resist expulsion or other migration through a defect,
or other opening, in the annulus fibrosis and to resist excessive
migration within an intervertebral disc space. In certain forms, these
implants combine the advantages of an injectable/in-situ curing implant
with a pre-formed implant. For example, a nucleus pulposus implant may
include a load bearing elastic body surrounded by an outer, preferably
resorbable or otherwise temporary, shell. The outer shell advantageously
anchors the elastic body within the intervertebral disc space. The
surface of the elastic body may include various surface features,
including various macro-surface patterns, and chemical or physical
modifications as described herein to further enhance fixation of the
implant. The surface features, such as the macro-surface patterns and
physical modifications, for example, are also expected to enhance
fixation of the elastic body to surrounding tissue such that, in certain
forms of the invention, no outer shell may be needed.

[0064] In other aspects of the invention, nucleus pulposus implants having
shape memory that are configured to allow extensive short-term manual or
other deformation without permanent deformation, cracks, tears, breakage
or other damage are provided. In preferred forms of the invention wherein
the implants are formed from a hydrogel or other hydrophilic material,
the implants can not only pass through a relatively small incision in the
annulus fibrosis, but can also substantially fill and conform to the
intervertebral disc space. In one form of the invention, an implant
includes a load bearing elastic body with shape memory having first and
second ends that are positioned adjacent to a central portion to form at
least one inner fold. The inner fold desirably defines an aperture or
channel.

[0065] In other embodiments of the invention, the shape memory implants
are configured to form a spiral or other annular shape in the disc space,
and may also be configured to have ends that matingly engage each other
for further securing the implant in the disc cavity. Methods of making
and implanting the implants described herein are also provided.

[0066] As disclosed above, in a first aspect of the invention, a nucleus
pulposus implant is provided that includes a load bearing elastic body
sized for introduction into an intervertebral disc space and surrounded
by an outer, preferably resorbable, shell. Referring now to FIGS. 1 and
2, prosthetic implant 10 includes a core load bearing elastic body 15
disposed in intervertebral disc space 20, between vertebral body 21 and
22 and surrounded by an outer shell 30. More specifically, elastic body
15 has an outer surface 16 in contact with, and preferably bonded to, an
outer shell 30 that may advantageously be resorbable, or otherwise
temporary. Outer surface 31 of outer shell 30 preferably conforms to the
shape of the intervertebral disc space 20, being in contact with annulus
fibrosis 5, and may completely surround elastic body 15 as seen in FIGS.
1 and 2, although outer shell 30 may only partially surround elastic body
15. As an example, upper, lower and/or lateral voids surrounding elastic
body 15 may be filled in by outer shell 30, as long as the elastic body
is in some way anchored, or otherwise fixed in place, by the outer shell
so as to prevent its expulsion from, or excessive migration in, the disc
cavity. Outer shell 30 may be configured to fill the aforementioned
voids. Additionally, inner surface 32 of outer shell 30 may conform to
the shape of elastic body 15, and may bond to outer surface 16 of elastic
body 15 as discussed below. In preferred embodiments, the elastic core
and the outer shell substantially fill the disc cavity as further
discussed below.

[0067] Outer shell 30 not only provides for a properly fit implant 10
within intervertebral disc space 20 for maximum load-bearing, stress
transfer, and bonding of the implant surface to the surrounding disc
tissues for fixation against excessive migration, it also seals an
annular defect 18 for further resistance to migration and/or expulsion of
the implant. Such sealing of the annular defect may also provide
additional physical and mechanical support to the disc. Furthermore, the
injectable outer shell material may provide intra-operative flexibility
in fitting the core elastic body of implant 10 within the disc space as
it may compensate for the differences in geometry and size between the
disc space and the pre-formed core.

[0068] Outer shell 30 is preferably resorbable and, in such form, is
preferably replaced with tissue, such as fibrous tissue and including
fibrous scar tissue, that may aid in permanently confining the load
bearing elastic body within the disc space. Referring now to FIGS. 3 and
4, tissue 33 has replaced outer shell 30, and thus surrounds elastic body
15. Although elastic body 15 may be confined within the disc space with
the aid of tissue 33, body 15 is expected to have some mobility for
normal biomechanics.

[0069] The dimensions of load bearing elastic body 15 may vary depending
on the particular case, but elastic body 15 is typically sized for
introduction into an intervertebral disc space. Moreover, elastic body 15
is preferably wide enough to support adjacent vertebrae and is of a
height sufficient to separate the adjacent vertebrae. In order to provide
long-term mechanical support to the intervertebral disc, the volume of
elastic body 15 in the disc space should be at least about 50%,
preferably at least about 70%, further preferably at least about 80%, and
more preferably at least about 90%, of the volume of the entire disc
space, the remaining volume occupied by outer shell 30. The volume of
elastic body 15 may be as large as about 99% of the volume of the
intervertebral disc space, and thus about 99% of the volume of implant
10. Accordingly, the volume of outer shell 30 may be at least about 1% of
the volume of the implant, but may range from about 1% to about 50%.

[0070] In some embodiments it is desired to increase the size of the disc
space by providing an implant and/or an implant/outer shell combination
that stretches and expands the disc space. For example, the implant
and/or implant/outer shell combination may be sized so that the maximum
implant volume is up to 130% of the vacated disc space. In other
preferred embodiments the implant and/or implant/outer shell combination
may be sized so that the maximum implant volume is up to 120% of the
vacated disc space, while in yet other preferred embodiments the implant
and/or implant/outer shell combination may be sized so that the maximum
implant volume is up to 110% of the vacated disc space.

[0071] The appropriate size of implant 10 desired in a particular case may
be determined by optionally distracting the disc space to a desired level
after the desired portion of the natural nucleus pulposus and any free
disc fragments are removed, and measuring the volume of the distracted
space, as for example, with an inflatable balloon filled with a saline
solution or a radiocontrast medium or other biomaterial. The balloon may
be expandable or non-expandable. Alternatively, the disc volume can be
measured directly by first filling the vacated disc space with a known
amount of saline or radiocontrast medium or other biocompatible material.
Various imaging techniques (e.g., X-ray, CT, MRI, NMR, etc.), preferably
with a reference scale, can be used to evaluate or measure the disc space
dimensions and/or volume and/or size.

[0072] Elastic body 15 may be fabricated in a wide variety of shapes as
desired, as long as the body can withstand spinal loads and other spinal
stresses. The non-degradable and preformed elastic body 15 may be shaped,
for example, as a cylinder, or a rectangular block. The body may further
be annular-shaped. For example, implant 10' in FIGS. 12 and 13 has a
spiral, or otherwise coiled, shape. The implant includes a first end 23
and a second end 24. Elastic body 15 may also be shaped to generally
conform to the shape of the natural nucleus pulposus, or may be shaped as
further described below. Although elastic body 15 is shown as one piece
in, for example, FIGS. 1-4, it may be made from one or several pieces.

[0073] Elastic body 15 may be formed from a wide variety of biocompatible
polymeric materials, including elastic materials, such as elastomeric
materials, hydrogels or other hydrophilic polymers, or composites
thereof. Suitable elastomers include silicone, polyurethane, copolymers
of silicone and polyurethane, polyolefins, such as polyisobutylene and
polyisoprene, neoprene, nitrile, vulcanized rubber and combinations
thereof. The vulcanized rubber described herein may be produced, for
example, by a vulcanization process utilizing a copolymer produced as
described, for example, in U.S. Pat. No. 5,245,098 to Summers et al. from
1-hexene and 5-methyl-1,4-hexadiene. Suitable hydrogels include natural
hydrogels, and those formed from polyvinyl alcohol, acrylamides such as
polyacrylic acid and poly(acrylonitrile-acrylic acid), polyurethanes,
polyethylene glycol, poly(N-vinyl-2-pyrrolidone), acrylates such as
poly(2-hydroxy ethyl methacrylate) and copolymers of acrylates with
N-vinyl pyrrolidone, N-vinyl lactams, acrylamide, polyurethanes and
polyacrylonitrile, or may be other similar materials that form a
hydrogel. The hydrogel materials may further be cross-linked to provide
further strength to the implant. Examples of polyurethanes include
thermoplastic polyurethanes, aliphatic polyurethanes, segmented
polyurethanes, hydrophilic polyurethanes, polyether-urethane,
polycarbonate-urethane and silicone polyether-urethane. Other suitable
hydrophilic polymers include naturally-occurring materials such as
glucomannan gel, hyaluronic acid, polysaccharides, such as cross-linked
carboxyl-containing polysaccharides, and combinations thereof. The nature
of the materials employed to form the elastic body should be selected so
the formed implants have sufficient load bearing capacity. In preferred
embodiments, a compressive strength of at least about 0.1 Mpa is desired,
although compressive strengths in the range of about 1 Mpa to about 20
Mpa are more preferred.

[0074] Outer shell 30 may be formed from a wide variety of biocompatible,
preferably elastic, elastomeric or deformable natural or synthetic
materials, especially materials that are compatible with elastic body 15.
The outer shell materials preferably remain in an uncured, deformable, or
otherwise configurable state during positioning of the elastic body in
the interverterbral disc space, and should preferably rapidly cure,
become harder or preferably solidify after being introduced into the
intervertebral disc space, or, in other embodiments, prior to positioning
of the elastic body in the intervertebral disc space. In preferred
embodiments, the outer shell materials may remain deformable after they
harden or otherwise solidify. Suitable materials that may be used to form
the outer shell include tissue sealants or adhesives made from natural or
synthetic materials, including, for example, fibrin, albumin, collagen,
elastin, silk and other proteins, polyethylene oxide, cyanoacrylate,
polyarylate, polylactic acid, polyglycolic acid, polypropylene fumarate,
tyrosine-based polycarbonate and combinations thereof. Other suitable
materials include demineralized bone matrix. These precursor materials
may be supplied in liquid, solution or solid form, including gel form.
Elastic body 15 may include a variety of surface features on outer
surface 16, including chemical modifications and surface configurations,
to provide surface features that advantageously improve the bonding
between outer surface 16 of the elastic body and inner surface 32 of
outer shell 30. In one form of the invention, outer surface 16 is
chemically modified utilizing, for example, chemical groups that are
compatible with the materials used to form outer shell 30. Suitable
chemical modifications include, for example, surface grafting of reactive
functional groups, including hydroxyl, amino, carboxyl and
organofunctional silane groups. The groups may be grafted by methods
known to the skilled artisan. Other modifications include pre-coating
with a primer, preferably one that is compatible with the outer shell
material, such as a layer of adhesive, sealing or other materials used
for forming the outer shell described above.

[0075] In yet another form of the invention, elastic body 15 may include
surface features, such as macro-surface patterns, or protuberances, as
seen in FIGS. 14A-14J, showing side views or top views of top portions of
elastic bodies with various surface features. Referring now to FIGS.
14A-14J, the pattern may be a dove-tail pattern 200, a circular pattern
205, a square pattern 210, a conical pattern 215, various wave patterns
220 and 225 and random, irregular patterns 230. In other embodiments, a
fiber 240 may be disposed in elastic body 241 and may project from the
surface 242 thereof to form a fibrous pattern 235. Fiber 240 may be
disposed as a loop projecting from the surface of the elastic body, its
ends may project from the surface of the elastic body, or the fiber may
have a wide variety of other appropriate configurations. The fiber may be
a short, polymeric fiber, such as one that is cut to less than about one
inch. The fiber may, alternatively, be a continuous polymeric fiber. The
fiber may further be braided, and may be woven or non-woven. The
macro-surface patterns are preferably formed during formation of elastic
body 15. However, outer surface 16 of elastic body 15 may also be
physically modified after formation of elastic body 15 by, for example,
laser drilling or thermal deformation. Physical modifications include,
for example, a microtexturized surface formed by bead-blasting, plasma
etching or chemical etching. Procedures for modifying various surfaces in
this manner are well known in the art.

[0076] In addition, surface features such as three-dimensional ("3-D")
porous surfaces may be provided for the portions of the nucleus implants
that contact adjacent surfaces such as endplates (or bony surfaces if
endplates are violated or removed) upon implantation. For example, a
three-dimensional porous surface may be provided by including a woven or
non-woven 3-D fabric or mesh with one side bonded to the upper or lower
surface of the nucleus implant and the other side free to contact the
bony tissues or endplates upon implantation. Such porous surfaces may
enable ingrowth of bony tissues and/or soft tissues for better fixation,
and may also provide increased friction for improved short-term or
long-term implant retention.

[0077] In one embodiment of a porous surface implant, the bonding between
the nucleus implant and the 3-D porous surface layer is enhanced by
having at least half of the thickness of the porous layer embedded in the
elastomeric material of the nucleus implant. This transition zone (the
portion of the elastomeric implant material that has the porous surface
layer material embedded in it) may be at least 0.5 mm thick, or may be as
thick as 7.5 mm.

[0078] In another embodiment the transition zones on both sides of the
nucleus implant are increased in size until they eventually overlap. This
creates a composite nucleus implant with 3 zones: 1) a 3-D porous upper
surface layer (0.5 mm up to 5 mm, preferably 1 mm to 3 mm thick); 2) a
transition zone (1 mm up to 15 mm, preferably 4 mm to 12 mm thick); and
3) a 3-D lower surface layer (same as or similar to the upper surface
layer).

[0079] Preferred embodiments of disc nucleus implant having porous
surfaces are described in the following Examples, which are illustrative
only, and are not intended to be limiting.

EXAMPLE 1

[0080] Porous upper and lower surface layers 611a and 611b are 1 mm thick
(no elastomeric material) and are provided on an intervertebral disc
nucleus implant 610 shown in FIG. 61. The transition zone 612 right below
the porous layers 611a and 611b continues throughout the implant and is
between 4 mm and 12 mm thick (elastomeric material embedded in porous
material). There is no center layer containing only elastomeric material.
The overall implant height or thickness is between 6 mm and 14 mm.

[0082] It is to be appreciated that the porous fabric or mesh can be made
of a polymeric, metallic or ceramic material or combinations thereof. The
porous fabric or mesh can be flexible/compressible,
semi-flexible/semi-compressible, or rigid. The mean pore size of the
porous surface may be between 50 microns to 2000 microns, and is
preferably between 100 microns and 1000 microns for good bony or soft
tissue ingrowth.

[0083] In certain forms of the invention, the implant may include only
elastic body 15 having one or more of the outer surface features as
described above, without the outer resorbable shell. The surface features
are expected to provide a certain level of fixation to the surrounding
tissues for improved resistance to migration and/or expulsion.

[0084] In yet other forms of the invention, the implant may include an
elastic body that is surrounded by a supporting, or otherwise
constraining, member wherein the supporting member is surrounded by a
resorbable shell as described herein. Referring now to FIG. 5, implant
400 includes a load bearing elastic body 15 that is surrounded by a
supporting member 34. In one form, supporting member 34 may be a
preferably flexible, peripheral supporting band that is disposed
circumferentially about elastic body 15 as seen in FIG. 5, leaving upper
and lower surfaces 35 and 36, respectively, of elastic body 15 free from
the supporting band.

[0085] As seen in FIG. 5, portions of upper and lower surfaces 35 and 36,
respectively, of elastic body 15 are exposed to directly contact outer
shell 30. This exposure minimizes the amount of material needed to
construct the supporting member, yet still effectively provides, for
example, lateral support. Although the amount of the upper and lower
surfaces of elastic body 15 that are exposed may vary, typically at least
about 50%, preferably at least about 70%, more preferably at least about
80% and most preferably at least about 90% of the surfaces are exposed.

[0086] In yet another embodiment shown in FIG. 6, nucleus pulposus implant
500, that includes elastic body 15 as described above, is reinforced with
supporting member 37, which takes the form of a jacket. The jacket
preferably completely surrounds elastic body 15.

[0087] Suitable supporting members, including reinforcing outer bands,
covers, or other jackets, may be formed from a wide variety of
biocompatible polymers, metallic materials, or combination of materials
that form a strong but flexible support to prevent excessive deformation,
including lateral (horizontal) deformation, of the core under increasing
compressive loading. Suitable materials include non-woven, woven,
braided, or fabric materials made from polymeric fibers including
cellulose, polyethylene, polyester, polyvinyl alcohol, polyacrylonitrile,
polyamide, polytetrafluorethylene, polyparaphenylene terephthalamide, and
combinations thereof. Other suitable materials include non-reinforced or
fiber-reinforced elastomers such as silicone, polyurethane, copolymers of
silicone and polyurethane, polyolefins, including polyisobutylene and
polyisoprene, neoprene, nitrile, vulcanized rubber, and combinations
thereof. In a preferred form of the invention, a combination, or blend,
of silicone and polyurethane is used. Furthermore, the vulcanized rubber
is preferably produced as described above for the nucleus pulposus
implants. Supporting members 34 and 37 are advantageously made from a
porous material, which, in the case of an elastic body made from a
hydrogel, or other hydrophilic material, allows fluid circulation through
the elastic core body to enhance pumping actions of the intervertebral
disc. Supporting members may further be formed from carbon fiber yarns,
ceramic fibers, metallic fibers or other similar fibers as described, for
example, in U.S. Pat. No. 5,674,295.

[0088] FIGS. 7A-7D show supporting bands of various patterns, typically
made from various braided materials (bands 25, 26 and 27), or porous
materials (band 28), as described above. It is also understood the
jackets may also be formed of such patterns. It is realized that the
braided materials may also be porous.

[0089] Supporting members 34 and 37 preferably decrease lateral
deformation, compared to deformation of an implant without the supporting
member, as desired. Supporting members 34 and/or 37 may, for example,
decrease lateral deformation by at least about 20%, preferably at least
about 40%, more preferably by at least about 60% and most preferably by
at least about 80%. An implant, such as one that includes an elastic
body, having such a supporting member will be flexible and otherwise
resilient to allow the natural movements of the disc and provides shock
absorption capability at low to moderate applied stress, but will resist
excessive deformation for disc height maintenance under high loading
conditions. In the case of a lumbar disc, for example, low applied stress
includes a force of about 100 Newtons to about 250 Newtons moderate
stress includes a force of about 250 Newtons to about 700 Newtons, and
high loading conditions, or high stress, includes a force of above about
700 Newtons. In preferred forms of the invention, the supporting member
is flexible, in that it may be folded, or otherwise deformed, but is
substantially inelastic, so that the implant is more fully reinforced or
otherwise supported.

[0090] The elastic body may be covered by the jacket supporting member, or
the band supporting member may be wrapped around the circumference of the
elastic body. In a form of the invention wherein the elastic body is
formed from a hydrogel, or similar hydrophilic material, the hydrogel may
be dehydrated a desired amount prior to being covered by the jacket, or
prior to wrapping the band around the circumference of the hydrogel body.
The hydrogel elastic body may be exposed to saline outside of the body,
or may be inserted into the disc space wherein it will be exposed to body
fluids in situ, and the body will absorb water and swell. In reference to
the peripheral band supporting member, the swelling or expansion of the
hydrogel elastic body in the horizontal direction is controlled by the
amount of slack designed in the band. After the limited allowable
horizontal expansion is reached, the elastic body is forced to expand
mostly in the vertical direction until reaching equilibrium swelling
under the in vivo load. As the upper and lower surfaces of the elastic
body are not substantially constrained, the vertical expansion is mainly
controlled by the applied stress and the behavior of the hydrogel
material.

[0091] In yet other forms of the invention, an implant reinforced with a
peripheral supporting band as described above that is surrounded by a
resorbable outer shell may be further reinforced with one or more straps.
The straps may be advantageous in preventing the peripheral supporting
band described herein from slipping, or otherwise sliding off the
implant. Referring now to FIGS. 8 and 9, at least one strap 420 extends
along upper surface 35 and at least one strap 430 extends along lower
surface 36 of elastic body 15 of implant 400. Ends 421 of strap 420 and
ends 431 of strap 430 are each preferably connected, or otherwise
attached, to peripheral supporting band 34'. The point of attachment may
be any location that will secure the strap, including at the upper
margins 138 of the band, lower margins 139 of the band or any region
between the upper and lower margins. Although two straps 420 and 430 are
shown extending along upper surface 35 and lower surface 36,
respectively, in FIGS. 8 and 9, one continuous strap may be utilized that
extends completely around the implant, or the strap utilized may be in
one, two or multiple pieces, as long as the combination of straps are
sufficient to prevent excessive slipping and or sliding of the supporting
band. Furthermore, more than one strap may extend along upper surface 35
and more than one strap may extend along lower surface 36 of elastic body
15, as seen, for example, in FIGS. 10 and 11 of implant 500, wherein
straps 520, 530, 540 and 550 are shown attached, or otherwise connect to
supporting member 34". It is realized that the straps may be present in
one or more pieces. For example, straps 520 and 530 may form a single
strap, as may straps 540 and 550, or may all combine to form a single
strap.

[0092] In other aspects of the invention, kits designed for forming the
intervertebral disc nucleus pulposus implants that include the outer
shell described above are provided. In one form, a kit may include a load
bearing elastic body as described above, along with a container of
material to form the outer, preferably resorbable, shell. The material
may be selected from the materials as described above. Also, the
container that houses the material that forms the shell may be made from
a wide variety of materials that are compatible with the outer shell
material, including glass and plastic. The kit may further include a
supporting member, such as a supporting band, jacket or other outer cover
as described above. Generally, the kits include sterile packaging which
secures the kit components in spaced relation from one another sufficient
to prevent damage of the components during handling of the kit. For
example, one may utilize molded plastic articles known in the art having
multiple compartments, or other areas for holding the kit components in
spaced relation.

[0093] In a further aspect of the invention, nucleus pulposus implants are
provided having shape memory that are configured to allow extensive
short-term manual, or other, deformation without permanent deformation,
cracks, tears, breakage or other damage, that may occur, for example,
during placement of the implant into an intervertebral disc space.
Referring now to FIGS. 15A and 16A, in one form of the invention, implant
40 includes a load bearing elastic body 41 with shape memory and having a
first end 42 and a second end 43 that are positioned adjacent to a
central portion 44 to form at least one inner fold 45. As shown in the
drawings, the ends may folded so that ends 42a and 43a abut without
overlapping. Inner fold 45 preferably defines at least one aperture 46
which is advantageously arcuate, but the apertures are small relative to
the size of the implant so that the center "core" of the implant is
substantially solid when the implant is in its first, folded
configuration. The elastic body is deformable, or otherwise configurable,
manually, for example, from this first folded, or otherwise relaxed
configuration shown in FIG. 15A into a second, substantially
straightened, or otherwise non-relaxed configuration shown in FIG. 16A
for placement into the intervertebral disc space. As elastic body 41 has
shape memory, it returns by itself, automatically, back into the first
folded, relaxed configuration once manual or other force is no longer
exerted on the body (in other words, the shape memory biases the implant
to its first configuration). These implants therefore provide improved
handling and manipulation characteristics in that they may be deformed,
configured and otherwise handled by an individual without resulting in
any breakage or other damage to the implant.

[0094] Further describing the shape memory nucleus prosthesis implant 40,
implant 40 includes surface depressions 47, or other surface
irregularities as more fully described below, that form inner fold 45
when the implant is in its relaxed configuration. Ends 42 and 43 have end
surfaces 42a and 43a, respectively, that are generally flat, and
substantially parallel, or perpendicular in other forms, to an axis X to
passing through the width of the implant in its relaxed configuration,
wherein the ends may abut each other without overlapping as seen in FIGS.
15A, 15B and 15E-15N. The ends of the implant may each alternatively abut
the central portion of the implant, as shown for implants 60 and 70 in
FIGS. 15C and 15D, respectively, to form a generally bi-lobed or
binocular-shaped implant.

[0095] Alternatively, in other forms of the invention, one end of the
implant may be tapered, or otherwise specifically shaped, and the other
end may be shaped complementary to the tapered, or otherwise shaped, end.
Moreover, either one or both sides 96a and 96b of the ends of the nucleus
pulposus implant may be tapered. For example, and as seen in FIGS. 15F
and 16F, both sides of end 93 of implant 90 are tapered to form a pointed
end, such as a generally V-shaped end, that advantageously fits into a
complementary-shaped (e.g., V-shaped) depression 95 defined by end 92. An
implant having only one inner fold that defines one aperture and ends
that are similarly configured as ends 92 and 93 is shown in FIGS. 15J and
16J. As another example, one side of each of the ends of the implant may
be oppositely tapered as seen in FIGS. 15G and 16G. That is, side 108a of
end 102 of implant 100 and opposite side 109b of end 103 are tapered as
seen in FIG. 15G and 16G. End surfaces 102a and 102b of implant 100 are
transverse to axis X when the implant is in its relaxed configuration
shown in FIG. 15G. In those embodiments where the ends of the implants
are tapered, or otherwise shaped, it is preferred that, when the ends of
the implants contact each other or the central or other portion of the
implant, an implant is formed that is uniform along the length of the
implant through the region of contact.

[0096] Although the implant may assume a wide variety of shapes, it is
typically shaped, in its folded, relaxed configuration, to conform to the
shape of the natural nucleus pulposus. Thus, the implants may be
substantially elliptical when in their folded, relaxed, configurations in
some forms of the invention. In yet further forms of the invention, the
shape of the implants in their folded configurations may be generally
annular-shaped or otherwise shaped as required to conform to the
intervertebral disc cavity. Moreover, when the implants are in their
unfolded, non-relaxed, configuration, such as their substantially
straightened configuration, they may also assume a wide variety of
shapes, but are most preferably generally elongated, and preferably
generally cylindrical, or other shape as described herein.

[0097] In yet other forms of the invention, the folding implant may have a
surface that includes surface features such as indents or projections
that further aid in allowing short-term deformation of the implant
without permanent deformation or other damage as described above.
Referring now to FIGS. 15D and 16D, implant 70 includes a load bearing
elastic body 71 having a first end 72, a second end 73 and a central
portion 74. Inner fold 75 defines an aperture 76 and includes an inner
fold surface 77 having wrinkles, indents, or projections 78 thereon.
Whether the surface feature is called a wrinkle, an indent, or a
projection is largely a matter of style, and depends primarily on one's
definition of where the "surface" lies. In all cases the surface feature
provides a change in the thickness of the implant at that point, to
relieve stress and prevent cracking or tearing of the implant when the
implant is straightened for implantation. Projections 78 of inner fold
surface 77 may extend into aperture 76. These wrinkles facilitate
stretching of the implant without deformation, cracking, tearing,
breakage, or other damage when the implant is straightened or elongated
for insertion into the intervertebral disc space. In the embodiment shown
in FIGS. 15D and 16D, the wrinkles, or surface projections, extend along
the entire length of elastic body 71, including central portion 74. Other
implants having wrinkled inner fold surfaces are seen in FIGS. 15E and
16E and other wrinkle configurations upon folding the implant are seen in
FIGS. 15K-15N and 16K-16N.

[0098] Other folding implants are shown in FIGS. 22A-22Q, 23A-23Q and
24-27. Referring to these figures, implants 400-620 are shown that have a
plurality of inner folds, ranging from, for example, two to about six.
Moreover, these implants, as well as the above-discussed folding
implants, have first and second ends that are formed from first and
second arms, respectively, of the implants. As seen in FIGS. 22A and 23A,
for example, first end 402 of implant 400 is formed from a first arm 408
connected to, or otherwise associated with, one end 404a of central
portion 404. Second end 403 is formed from a second arm 409 connected to,
or otherwise associated with, opposing end 404b of central portion 404.
Surface depressions 405 or other surface irregularities define inner
folds 406 when the implant is in its relaxed configuration.

[0099] In certain forms of the invention, each of the arms connected to
the central portions of the implant are the same length, as seen in FIGS.
15A-15J, 15L-15N, 22A-22B, 23A-23B, 22D-22E, 23D-23E, 22G and 23G. In yet
other forms of the invention, one of the arms is shorter than the other
arm. For example, as seen in FIG. 22C, second arm 429 of implant 420 is
shorter than first arm 428, wherein each arm is connected to an end of
central portion 424. Stated alternatively, in certain forms of the
invention, the ends of the implant abut each other along a plane
extending along axis X and passing through the width of the implant,
resulting in a center or central closure C of the implant as seen, for
example, in FIG. 22A. In other forms of the invention, the ends of the
implant abut each other along a plane extending parallel to a plane
extending along axis X and passing through the width of the implant,
resulting in an off-center closure C' of the implant as seen, for
example, in FIG. 22C. The differential length of the arms of the implants
can facilitate implantation and proper positioning of the implants in the
disc space as more fully described below.

[0100] Moreover, some of the inner folds of the implants may be formed
when the first end and the second end of the implant contact, or
otherwise abut, each other, as seen, for example, in FIG. 22C. In such
forms of the invention, each end of the implant may include a surface
that has a surface depression, such as surface depression 421 or 422, as
seen in FIG. 23C, that forms a portion of the inner fold such that when
the ends of the implant contact each other, an inner fold is formed from
the combination of surface depressions. Additionally, the apertures
defined by the inner folds may have a variety of cross-sectional shapes,
including substantially annular or otherwise ring-shaped, substantially
oval or otherwise elliptical-shaped, star-shaped or other various shapes
known to the skilled artisan. The star-shaped pattern includes a
plurality of finger-like or otherwise elongated projections 465 or 475 as
seen, for example, in FIGS. 22G and 22H, respectively.

[0101] FIGS. 22I, 23I, 24, 22K, 23K and 26 show further details of
implants of the present invention. For example, apertures, or channels,
486 and 506, can be seen in FIGS. 24 and 26, respectively, showing
implants 480 and 500, respectively. Turning now to FIGS. 22J, 23J and 25,
implant 490 is shown that includes all of the features of the
aforementioned implants, including a load bearing body 491, a first arm
498 having a first end 492, a second arm 499 having a second end 493, and
surface depressions 497. Additionally, implant 490 includes a central
portion 494 that extends along the full width of implant 490 from one end
of the implant to an opposing edge of the implant. In such an embodiment,
end surfaces 492a and 493a abut, and are otherwise in contact with,
central portion 494 when implant 490 is in its folded configuration as
seen in FIG. 22J.

[0102] In one form of the invention, at least one end of the implants may
be curved, or otherwise arcuately-shaped or rounded. Referring to implant
510 in FIGS. 22L and 23L, first end 512 and second end 513 each have an
inner edge 512b and 513b, and an outer edge, 512a and 513a, respectively.
Outer edges 512a and 513a are shown as rounded and can facilitate
implantation and proper positioning of the implants in the disc space as
more fully described below.

[0103] For example, the rounded edges allow for better conformity of the
implant to the disc space. Although not being limited by theory, it is
believed that the dome-shaped, or otherwise concave-shaped, endplates may
lead to increased stress concentrated at the edges of the implant. The
rounded edges reduce such stress. In this manner, there is a smaller
likelihood of the implant penetrating the endplate, and the durability of
the implant is improved. Bone remodeling based on the shape of the
implant is also reduced.

[0104] Referring to FIGS. 22M and 23M, implant 610 is shown wherein both
ends of the implants have edges that are curved or otherwise rounded.
Implant 610 includes body 611 having first arm 613 and second arm 614.
First arm 613 and second arm 614 include ends 613a and 614a,
respectively, which both preferably have rounded edges 613b and 614b,
respectively, although only one of the ends may have such a rounded,
straight or other shaped edge. In this embodiment, end 614a of second arm
614 is tapered, or otherwise has a decreased diameter compared to end
613a of first arm 613. Additionally, first arm 613 is shorter than second
arm 614.

[0105] Referring to FIGS. 22N-22Q, 23N-23Q and FIG. 27, alternative
embodiments of the above-described folding implants are shown. As with
all of the implants, the bodies forming the implants have a top surface T
for contacting an upper vertebral endplate of an intervertebral disc and
a bottom surface B for contacting a lower vertebral endplate of the
intervertebral disc as seen, for example, in FIG. 27. Additionally, the
implants have an external side surface E that includes at least one
groove G extending along the side surface that advantageously further
relieves the compressive force on the external side E of the implant when
the implant is deformed into a substantially straightened, or otherwise
unfolded configuration and thus further allows extensive short-term
deformation without permanent deformation, cracks, tears or other
breakage. For example, implant 620 shown in FIGS. 22N, 23N and 27
includes a load bearing body 621 that has a top surface T, a bottom
surface B, an internal side surface I and an external side surface E. A
plurality of grooves G are disposed along external side surface E that
typically extend from the top surface to the bottom surface of the
implant. When dividing the implant in half, thus more easily viewing a
first side S.sub.1 and a second side S.sub.2, with a plane passing
through the width of the implant along axis X, it can be seen in FIG. 22N
that four grooves G are present on first side S.sub.1 and four grooves G
are present on second side S.sub.2, although more or less may be present
depending on the case. It is preferred that at least one groove is
present on each side S.sub.1 and S.sub.2.

[0106] FIGS. 22O and 23O depict implant 570, which is similar to implant
620, with the exception that implant 570 includes a second arm 572 that
is smaller than first arm 571, resulting in an off-center closure C' as
more fully described above. FIGS. 22P and 23P depict implant 610' and
FIGS. 22Q and 23Q depict implant 490', which are identical to implants
610 and 490, respectively, with the exception that implants 490' and 600'
both include external side grooves G as described herein.

[0107] In yet other preferred forms of the invention, the top and bottom
contact surfaces of the implants are configured to be complementary to
the top and bottom endplates of an intervertebral disc, respectively. For
example, the top and bottom contact surfaces of the implants may be
convex, to conform to the respective concave intervertebral disc
endplates. Additionally, although the implants are preferably one-piece
implants, they may also be composed of one or more pieces. For example,
an implant may be composed of a separate central portion and first and
second arms, wherein the arms are associated or otherwise attached to the
central portion as described herein.

[0108] In certain preferred forms of the invention, the apertures defined
by the inner folds of the implants described above have a radius of at
least about 1 mm. Moreover, in other preferred forms of the invention, a
reinforcing material may be included at the inner fold surface to further
improve the structural integrity of the implant. The reinforcing material
may be a fabric that is either woven, or non-woven, and may be formed
from braided fibers for further strength. The reinforcing material may be
positioned on the inner fold surface, may project therefrom or may be
entirely embedded under the inner fold surface. The implant may be formed
as a single piece, or may be formed of more than one piece that is
connected to the other pieces that form the assembled implant by fabric
that may be made from braided or other fibers, or may be connected by
some other components or manner, such as by use of adhesives, or other
methods of connecting such components together. Although these implants
are designed to be used without an anchoring outer shell, they, as well
as all of the implants described herein, may form the core elastic body
of an implant that includes the outer shell described herein.

[0109] The implants may obtain their shape memory characteristics in a
variety of ways. For example, the implants may be formed in a mold into a
desired final shape, and, when deformed from this final shape by
application of an external force, will return to the final shape upon
release of the force.

[0110] In yet another embodiment of the invention, a nucleus pulposus
implant is provided that has a locking feature, with optional shape
memory characteristics, and thus may also resist being expelled from the
disc cavity to some extent. In one form of the invention as seen in FIGS.
17-19, an implant 300 includes a load bearing elastic body 301 having a
first end 302 and a second end 303. The ends are typically configured for
mating engagement with each other. Elastic body 301 has a first, locked
configuration wherein first end 302 and second end 303 are matingly
engaged to each other as seen more particularly in FIG. 17. When elastic
body 301 has shape memory characteristics, elastic body 301 is
deformable, manually, for example, into a second, substantially
straightened, non-relaxed configuration for insertion into an
intervertebral disc space, as seen in FIG. 19, and may automatically be
configured or otherwise returned back into the first, locked, relaxed
configuration after insertion due to its shape memory characteristics. In
those cases where the elastic body does not have shape memory
characteristics and the elastic body is configurable into a locked and/or
straightened configuration, and in those cases where the elastic body has
shape memory characteristics, the elastic body may also be placed into
its locked configuration with the assistance of external force.

[0111] More particularly describing one form of the invention, end 302
defines an internal channel 304 as seen in FIG. 19 whereas end 303 is
configured to conform to the shape of internal channel 304. The channel
may take the form of a wide variety of shapes, as long as the ends of the
elastic body may be matingly engaged to form a locked configuration. As
seen in FIG. 19, the channel is somewhat hour-glass shaped. Manual, or
other force, may be applied to end 303 so that it may be temporarily
deformed, or configured, sufficiently to pass through narrowed passage
305 within internal channel 304. Once properly positioned, end 303 will
be secured within channel 304, as end edges 303a and 303b are braced
against channel edges 304a and 304b, respectively. Alternatively, one end
of an implant with a locking feature may be friction-fit within the
internal channel present in the other end of the implant. The
friction-fit may arise as a result of the relative size differences
between the inner diameter of the channel formed by one end and the outer
diameter of the other end of the implant. Additionally and/or
alternatively, the outer surface of one end, and/or the inner surface of
the channel defined by the other end, may include surface features as
described herein that aid in achieving the friction-fit. The implant may
also be constructed from the biocompatible polymeric materials as
described above.

[0112] When the implants are formed from an elastic material, such as a
hydrogel, or other similar hydrophilic material, or include the
resorbable outer shell, they may advantageously deliver desired
pharmacological agents. The pharmacological agent may be a growth factor
that may advantageously repair the endplates and/or the annulus fibrosis.
For example, the growth factor may include a bone morphogenetic protein,
transforming growth factor-.beta. (TGF-.beta.), insulin-like growth
factor, platelet-derived growth factor, fibroblast growth factor or other
similar growth factor or combination thereof having the ability to repair
the endplates and/or the annulus fibrosis of an intervertebral disc.

[0113] The growth factors are typically included in the implants in
therapeutically effective amounts. For example, the growth factors may be
included in the implants in amounts effective in repairing an
intervertebral disc, including repairing the endplates and the annulus
fibrosis. Such amounts will depend on the specific case, and may thus be
determined by the skilled artisan, but such amounts may typically include
less than about 1% by weight of the growth factor. The growth factors may
be purchased commercially or may be produced by methods known to the art.
For example, the growth factors may be produced by recombinant DNA
technology, and may preferably be derived from humans. As an example,
recombinant human bone morphogenetic proteins (rhBMPs), including rhBMP
2-14, and especially rhBMP-2, rhBMP-7, rhBMP-12, rhBMP-13, and
heterodimers thereof may be used. However, any bone morphogenetic protein
is contemplated including bone morphogenetic proteins designated as BMP-1
through BMP-18.

[0114] BMPs are available from Genetics Institute, Inc., Cambridge, Mass.
and may also be prepared by one skilled in the art as described in U.S.
Pat. Nos. 5,187,076 to Wozney et al.; 5,366,875 to Wozney et al.;
4,877,864 to Wang et al.; 5,108,922 to Wang et al.; 5,116,738 to Wang et
al.; 5,013,649 to Wang et al.; 5,106,748 to Wozney et al.; and PCT Patent
Nos. WO93/00432 to Wozney et al.; WO94/26893 to Celeste et al.; and
WO94/26892 to Celeste et al. All bone morphogenic proteins are
contemplated whether obtained as above or isolated from bone. Methods for
isolating bone morphogenetic protein from bone are described, for
example, in U.S. Pat. No. 4,294,753 to Urist and Urist et al., 81 PNAS
371, 1984.

[0115] In other forms of the invention, the pharmacological agent may be
one used for treating various spinal conditions, including degenerative
disc disease, spinal arthritis, spinal infection, spinal tumor and
osteoporosis. Such agents include antibiotics, analgesics,
anti-inflammatory drugs, including steroids, and combinations thereof.
Other such agents are well known to the skilled artisan. These agents are
also used in therapeutically effective amounts. Such amounts may be
determined by the skilled artisan depending on the specific case.

[0116] The pharmacological agents are preferably dispersed within the
hydrogel, or other hydrophilic, implant for in vivo release, and/or, with
respect to the implants with the resorbable outer shell, may be dispersed
in the outer shell. The hydrogel can be cross-linked chemically,
physically, or by a combination thereof, in order to achieve the
appropriate level of porosity to release the pharmacological agents at a
desired rate. The agents may be released upon cyclic loading, and, in the
case of implants including a resorbable outer shell, upon resorption of
the shell. The pharmacological agents may be dispersed in the implants by
adding the agents to the solution used to form the implant, by soaking
the formed implant in an appropriate solution containing the agent, or by
other appropriate methods known to the skilled artisan. In other forms of
the invention, the pharmacological agents may be chemically or otherwise
associated with the implant. For example, the agents may be chemically
attached to the outer surface of the implant.

[0117] Methods of forming and implanting the nucleus pulposus implants
described herein are also provided. In one form of the invention, with
respect to implant 10 described above having the anchorable outer shell
30, implant 10 may be formed by first forming elastic body 15 and then
forming the outer shell. Methods of forming elastic body 15 are well
known in the art.

[0118] For example, if the elastic body is made of elastomeric materials,
such as powdered elastomers including, for example,
styrene-ethylene/butylene block copolymers, the powdered elastomer may be
placed into an appropriate mold and may be compressed and heated to melt
the powder. The mold is then cooled to room temperature. If the elastic
body is made from a hydrogel, such as a polyvinyl alcohol, the polyvinyl
alcohol powder may be mixed with a solvent, such as, for example, water
or dimethylsulfoxide, or combinations thereof, and heated and shaken
until a uniform solution is formed. The solution may then be poured into
a mold, such as a rubber mold, and may be cooled at an appropriate
temperature, such as about 0.degree. C. to about -80.degree. C., for
several hours to allow for crystallization. After cooling, the hydrogel
can be partially or completely hydrated by soaking and rinsing with water
but, in certain preferred embodiments, may remain dehydrated so that it
may be inserted through a smaller aperture in the annulus fibrosis.

[0119] As to the general or preferred surgical techniques, prior to
positioning the implant in the interverterbral disc space, an incision
may be made in the annulus fibrosis, or one may take advantage of a
defect in the annulus, in order to access the disc space. In some
embodiments a K-wire is used to puncture the disc annulus to prepare it
for dilation. A first dilator, such as a 1.0 to 2.0 mm dilator, is used
to make the initial hole in the annulus, and a series of dilators of
increasing size are used until the hole is, for example, 5.0 to 7.0 mm
wide. A ronguer or other instrument (e.g., an ablation instrument or a
powered tissue remover) may be used to remove all or part of the natural
nucleus pulposus and any free disc fragments within the intervertebral
disc space. The disc space may then be distracted to a desired level by
distractors or other devices known to the skilled artisan for such
purposes.

[0120] It is important to measure the size of the disc space so that the
appropriate size of implant may be selected. As described above, the
measurement may be done directly by filling the space with a saline
solution or other biocompatible material, which is preferably injected.
By measuring the amount of material that is injected into the space, the
volume of the vacated disc may be determined. Alternatively, an
inflatable balloon may be used to avoid direct contact of the saline or
other material with the patient's tissue. The balloon may be filled with
saline solution or other material and the volume of the material used may
be measured to determine the volume of the disc space. When a
radiocontrast material is used the dimensions of the disc space may also
be determined by diagnostic techniques such as A/P and/or lateral X-rays,
CT, NMR, or MRI. Methods of using an inflatable balloon to facilitate
implantation of an intervertebral disc implant are disclosed in
applicant's application Ser. No. 10/314,396, filed Dec. 4, 2002, the
entire contents of which is incorporated herein by reference.

[0121] Once the size and/or dimensions of the disc space have been
determined, the surgeon may select the appropriate implant size and
shape. Accordingly, and while recognizing that it may be desirable to
select an implant size that is larger or smaller than the size of the
disc space for reasons stated herein, the surgeon may tentatively select
an implant height according to the height of the disc as indicated by a
diagnostic X-ray or other means of diagnosis (e.g., with or without an
inflatable balloon) as mentioned above. Then, an appropriate footprint
size is selected according to the anterior and posterior widths indicated
by the diagnostic X-ray (or other means of diagnosis). A template or
chart indicating the appropriate implant size for given disc sizes and/or
volumes may be used if desired. If the surgeon determines that the disc
space should be increased for proper implant sizing, additional nucleus
removal may be done to accomplish that end. Alternatively, as described
below, additional material such as collagen-rich material or an
injectible filler may be used to augment the implant to better match the
available disc size and shape.

[0122] Once the appropriate implant is selected, the implant may be
inserted through a small surgical incision, puncture, slit, or x-shaped
cut made in the annulus. In other embodiments the implant is inserted
through a hole that has been made in the annulus, such as a round or
square or oval hole made by coring and removing a small plug from the
annulus fibrosis. In all embodiments the incision or hole may be
distended by using a series of dilators to dilate the opening to a size
large enough to accommodate the implant, as mentioned above. Moreover,
and as previously indicated, a guide wire, such as a K-wire, may be used
as an initial guide for one or more of the dilators. Generally, the
smallest opening that enables delivery of the implant through the annulus
into the disc space is preferred. Also, methods of providing an opening
for implant delivery that minimize the amount of tissue that is removed
are preferred. In most cases, healing or closing of the disc annulus
defect is facilitated by minimizing the size of the cut and the amount of
tissue removed.

[0123] Once formed, and after preparing the disc space for receiving the
implant, elastic body 15 may be implanted into the intervertebral disc
space utilizing devices well known in the art and as described in U.S.
Pat. Nos. 5,800,549 and 5,716,416. If the outer shell precursor material
was already placed in the intervertebral disc space, excess precursor
material may flow out of the disc space. This excess material should be
promptly removed before it sets or otherwise cures. The outer shell
material may be injected, or otherwise introduced, into the disc space
utilizing devices that are well known in the art, such as syringes,
sealant/caulk guns, automatic liquid injectors, and applicators that
include, for example, two separate syringes which allow for simultaneous
mixing of the components in a static mixer and delivery to the site, and
may be injected either prior to or after introduction of the implant into
the disc space. Whether the outer shell material is introduced prior to
or after introduction of the implant into the disc space, the distractor
is then removed, any excess precursor material seeping out of the disc
space is removed and the precursor material within the disc space is
cured to form the outer shell. It is noted that the elastic body may
already be surrounded by the outer shell, which may be in a partially or
fully hardened state but preferably remains deformable, prior to
introducing the elastic body into the intervertebral disc space.

[0124] In further aspects of the invention, spinal disc implant delivery
devices, or tools, are provided to be used in preferred methods of
implanting the implants described herein, especially the shape memory
implants. In one form, the device preferably includes an elongated member
having a lumen extending longitudinally therethrough for loading of the
desired implant, a tip portion for controlling passage of the implant out
of the delivery tool and a plunger or other elongated member or other
device for pushing the implant through the tool and into an
intervertebral disc cavity. The tip portion preferably includes a movable
member that may be moved from a first, closed position in which it blocks
the passage of a spinal disc implant through the lumen, and out of the
distal end, of the elongated member into which the spinal implant is
loaded and otherwise housed. The tip portion may also preferably be moved
to a second, open position, wherein egress of the spinal implant is
allowed.

[0125] Referring to FIG. 28, device 700 includes an elongated member 701,
such as a syringe housing 702 or other elongated housing or barrel that
defines a cavity, or lumen, 703 that extends along its length, and has a
proximal end 704 and a distal end 705. Proximal end 704 defines a flange
704a. Inner surface 703a of cavity, or lumen, 703 is preferably
configured for passage of a spinal nucleus pulposus implant. For example,
inner surface 703a is preferably smooth. Although elongated housing
member 701 is shown in FIG. 29 as having a square cross-sectional shape,
the cross-sectional shape of housing member 701 may vary along its length
and may be selected from a wide variety of geometric shapes, including
elliptical, circular, rectangular, hexagonal or other multi-sided shape
or a combination thereof. Device 700 further includes a plunger 706, or
elongated or other member. Plunger 706 includes an elongated member, or
rod, 720 having proximal end 707 and distal end 709 that may be utilized
to push a nucleus pulposus implant that may be disposed in cavity 703
through the housing and ultimately into an intervertebral disc space.
Distal end 709 of plunger 706 may include a plunger tip 721 that is
configured to contact an implant during extrusion. The cross-sectional
shape of plunger tip 721 is preferably similar to that of elongated
housing member 701. Proximal end 707 of plunger 706 includes a plunger
handle 722. Plunger 706 may include one or more components that may
facilitate extrusion of the implant by pneumatic, hydraulic or mechanical
force, or by manual pushing or impacted force. For example, the plunger
can be in the form of a pushing or impacted plunger, a syringe plunger, a
caulk gun plunger, or a screw-driven plunger as known in the art.

[0126] Device 700 further includes component, or tip portion, 710 having a
proximal end 713 and a distal end 712 wherein tip portion 710 may be
integral or detachable. For example, proximal end 713 of tip portion 710
may be matingly engageable to, or is otherwise connected or associated
with, distal end 705 of housing 702 of member 701. In one form of the
invention depicted in FIG. 29, tip portion 710 may include a top wall
730, a bottom wall 735, a side wall 740 and an opposing side wall 745.
Tip portion 710 defines a cavity, or lumen, 731 extending longitudinally
therethrough wherein lumen 731 is continuous, and otherwise in fluid
communication, with lumen 703 of elongated housing member 701.

[0127] The dimensions of tip portion 710, such as height H and width W,
may be configured to accommodate a spinal disc implant to be delivered.
Height H of tip portion 710 may have a height similar to or larger than
the disc space height depending on whether disc space distraction is
required. Additionally, length L of the tip portion may be chosen so that
tip portion 710 will preferably not substantially extend past the inner
wall of the annulus fibrosus as described more fully below. Different
dimensions of the tip portion may be determined by the skilled artisan.

[0128] Tip portion 710 is preferably configured to enter an aperture in an
annulus fibrosus for delivery of a spinal nucleus pulposus implant or
other spinal implant. Although tip portion 710 is shown as a rectangular
tube in FIG. 29, it may have a wide variety of shapes, including
cylindrical, square, hexagonal or other multi-sided shape. Surface 732 of
top wall 730 and surface 733 of bottom wall 735 contact the endplates
during delivery of the implant, and may have surface features 738 that
help anchor, engage or otherwise secure the tip to the opposing
endplates. Examples of such surface features, such as surface
roughenings, are shown in FIGS. 30A-30J and include teeth 738c-738g, in
the form of serrations or spikes (FIGS. 30C-30H), ridges 738i and 738j
(FIGS. 30I and 30J) a textured surface 738b (FIG. 30B) or a non-textured
surface 738a (FIG. 30A). The teeth or ridges may be directional and may
restrict movement in a single direction, such as seen in FIGS. 30D, 30E,
30F and 30G.

[0129] In yet another form of the invention, one side wall may be shorter
than the other to aid delivery and placement of the spinal disc implants
described herein. Referring to FIG. 31, delivery device 700a includes tip
portion 710a having side wall 740a that is shorter than side wall 745a.
FIG. 32 shows one way in which delivery of an implant 40 is aided. For
example, as implant 40 exits the device, it veers to the shorter side
wall and will subsequently fold up in the disc space.

[0130] In a further form of the invention, the top and bottom walls of the
tip portion may be partially open to alleviate any possible constriction
of the implant as it exits the device and is delivered into a disc space.
For example, referring to FIG. 33, tip portion 710' of device 700' may
include a top wall 730' having an opening 739 and a bottom wall 735'
having an opening 741, wherein both openings may extend from a proximal
end 712' to a distal end 713' of tip portion 710'. In such a fashion, tip
portion 710' forms opposing arms 736 and 737, each having an inner
surface I and an outer surface O. Inner surfaces I are preferably concave
and preferably accommodate a spinal disc implant.

[0131] Although both arms 736 and 737 of tip portion 710' are shown in
FIG. 33 as having the same length, one of the arms may be shorter than
the other to, for example, aid placement of the folding implants
described herein. For example, as seen in FIG. 34, arm 736' of tip
portion 710" of device 700" is shorter than arm 737'.

[0132] In yet another embodiment of a spinal disc implant delivery device,
one of the arms of the tip portion may be movable and the other
non-movable or otherwise stationary. As seen in FIG. 35, for example, arm
737" of tip portion 710"' of device 700"' is similar in configuration as
arm 737' and is preferably non-movable and further preferably otherwise
rigid. Arm 736" may also be non-movable or otherwise rigid, but it may
include both a non-movable portion 736a" and a movable, flexible or
otherwise elastic portion 736b" so that arm 736" may move, or be bent,
and form a closed configuration. For example, by appropriately
positioning arm portion 736b", arm 736" may be bent, preferably at an
angle .alpha. of greater than about 30.degree., further preferably
between about 45.degree. to about 90.degree., and typically about
60.degree.. It is preferred, especially when the tip portion also
functions as a distractor, that the movable portion of the arm has a
height that is less than the height of a disc space, and/or the height of
the arm at its distal end is shorter than at its proximal end, so that it
may move freely. In the closed configuration, the width W of distal end
713"' of tip portion 710"' is narrow, such as about 2 mm to about 10 mm,
which makes it easier to guide the tip portion into a small annular
opening. Additionally, the implant for delivery will be blocked from
exiting the delivery device by arm 736" in its closed configuration.

[0133] After the tip portion is inserted into the disc space, movable arm
736" may be moved, radially, for example, to form an open configuration,
such as the configuration of arm 736 of device 700' of FIG. 33, under
extrusion pressure to expand the annular opening and to allow the implant
to exit the device and enter the disc space as described below. After the
implant is delivered to the disc space, the movable arm retracts, bends
or otherwise moves back to its closed configuration in order to decrease
the expansion of the annular opening. It is realized that both arms may
also be rigid, flexible or otherwise elastic as desired. Other tip
portions that have such open and closed configurations are described
below. In preferred embodiments of the spinal disc implant delivery
devices described herein, the tip portion has wall support for the top,
bottom and side surfaces of the spinal disc implants to be delivered. It
is further noted that lumens 703', 703", 703"' of elongated members 701',
701" and 701"', respectively, are continuous, and in fluid communication,
with cavity 731', 731", 731"', respectively.

[0134] In yet another form of the invention, and referring to FIG. 36, a
spinal disc implant delivery device 800 includes an elongated member 801,
such as a syringe housing 802 that defines a cavity 803, and has a
proximal end 804 with a flange portion 804a and a distal end 805. Device
800 further includes a plunger 806, or elongated or other member, having
proximal end 807 and distal end 809 that may be utilized to push a
nucleus pulposus implant that may be disposed in cavity 803 through the
housing, out of the distal end of the housing and ultimately into an
intervertebral disc space.

[0135] Device 800 further includes component, or tip portion, 810 having a
proximal end 813 and a distal end 812, wherein proximal end 813 is
matingly engageable to, or is otherwise connected or associated with,
distal end 805 of housing 802 of member 801 which is also seen in FIG.
36. Tip portion 810 preferably includes a base member 850 which has a
proximal end 851, a distal end 852, and a lumen 853 extending
longitudinally therethrough. Tip portion 810 further preferably includes
at least one movable member that may form a closed configuration as
described herein. In preferred forms of the invention, tip portion 810
includes a plurality of movable members 880. Proximal end 881 of movable
members 880 abut, or are connected to or are otherwise associated with,
distal end 852 of base member 850.

[0136] Movable members 880 have a first, closed configuration wherein they
define a channel or cavity 883. The members may further have a closed
configuration which includes a narrowed distal end. Lumen 853 of base
member 850 and cavity 883 are preferably in fluid communication. Lumen
853 of base member 850 and cavity 803 of housing 802 are also preferably
in fluid communication when distal end 805 of housing 802 and proximal
end 851 of base member 850 are matingly engaged. In their closed
configuration, movable members 880 preferably further define an aperture
884, or other opening, at their distal end as best seen in FIG. 37A.
Aperture 884 is preferably sized and/or configured for ease of insertion
of the tip into an annular opening, preferably an undersized or
relatively small annular opening. For example, the diameter of aperture
884 of movable members 880 may range from about 2 mm to about 10 mm in
its closed configuration.

[0137] Movable members 880 are preferably movable, flexible, or otherwise
elastic, but in certain forms of the invention may be otherwise rigid,
and further have an open configuration wherein movable members 880 are
moved, flexed or otherwise bent sufficiently to enable passage of a
spinal implant, such as a nucleus pulposus implant described herein,
through lumen 853 of base member 850 and through an area circumscribed by
the movable members in their open configuration so that the spinal
implant may exit the delivery tool and may be inserted into or otherwise
positioned in an intervertebral disc space. Movable members 880 are
preferably placed in their open configuration when, for example, a spinal
implant is positioned in housing 802 of syringe 801 and plunger 806, or
other elongated or similar member, transmits a force sufficient for
translation of the spinal implant through cavity 803 of housing 802,
lumen 853 of base member 850 and cavity 884 defined by movable members
880. Contact of the inner surfaces of movable members 880 with, and
continued translation of, a spinal implant toward distal end 812 of
device 800 forces the radial flexing, bending or movement of movable
members 880 as described below.

[0138] Movable members 880 and base member 850 may be engaged, connected
or otherwise associated with each other in a variety of ways, including
use of an adhesive. Moreover, movable members 880 and base member 850 may
be integral. Base member 850 may also be integral with syringe housing
802, or may be attached by adhesive or other manner of attachment
described herein and/or known to the skilled artisan. For example, base
member 850 may have an inner surface 854 defining lumen 853 that is
tapered as desired to varying degrees so that base member 850 may be
associated with syringe housing 802 by friction fit. Other mechanical
interlocking methods known to the art may also be utilized to couple
proximal end 851 of base member 850 to distal end 805 of housing 802 of
syringe 801.

[0139] Tip portion 810 may include a plurality of movable members and may
assume a wide variety of shapes. As seen in FIG. 37A, tip portion 810 is
round and includes 16 movable members 880, although more or less may be
present as desired. For example, the tip portion may include 8 movable
members 780b, 780c and 780d (tip portion 810b-810d, respectively) as seen
in FIGS. 37B-37D, 4 movable members 780e (tip portion 810e) as seen in
FIG. 37E or 2 movable members 780f (tip portion 810f) as seen in FIG.
37F. Additionally, the movable members may contact a neighboring movable
member or may be variously spaced apart. For example, FIGS. 37D, 37E and
37F show movable members, which may be spaced apart by space S. Also, the
tip portions may assume a wide variety of cross-sectional shapes,
including circular, elliptical, square, rectangular or other multi-sided
or geometric shape.

[0140] The housing members, plunger members and base members described
herein may be made from a variety of materials, including metals known to
the art, such as stainless steel and titanium alloys, polymers known to
the art, including polyethylene, polypropylene, polyetheretherketone and
polyacetal. Movable members, such as movable members 880, may also be
made from a variety of materials, preferably those which are flexible or
otherwise elastic, and allow for flexing, bending or pivoting. Movable
members 880 may be made from the same materials as the housing members,
plunger members and base members described herein.

[0141] In yet another form of the invention, a method for implanting a
prosthetic intervertebral disc having shape memory is provided. In one
embodiment, an implant including a load bearing elastic body having a
first end and a second end positioned adjacent to a central portion to
form at least one inner fold as described above is provided. As mentioned
previously herein, the disc space may be distracted if necessary and all
or a portion of the nucleus pulposus may be removed. The implant 40, for
example, may be deformed by, for example, manual force into a
substantially straightened, non-relaxed configuration for insertion
through an aperture formed in the annular fibrosis as indicated in FIG.
20, and as best seen in FIG. 21. The aperture may be formed through
deterioration or other injury to the annulus fibrosis, or may be made by
purposely incising the annulus. The implant may then be positioned in a
delivery tool 310 known in the art, such as that described in U.S. Pat.
No. 5,716,416, and inserted through aperture 18 in annulus 19, although
utilization of the delivery devices or tools described more fully herein
is preferred. As the implant enters the intervertebral space 20 and is no
longer subject to manual force, it deforms back into its relaxed, folded
configuration as seen in FIG. 21. A portion, or substantially all, of the
natural nucleus pulposus may be removed from the intervertebral disc
space, depending on the circumstances, prior to introduction of the
implant into the intervertebral disc space. When implanting an implant
that includes a locking feature, or other implant with shape memory as
described herein, a similar protocol is followed. Additionally, with
respect to an implant with a locking feature, the implant may be placed
into the locked configuration with external force, imposed by, for
example, medical personnel. It is noted that, due to the symmetrical
features of a variety of the implants described herein, the implant may
be inserted into the disc space by a wide variety of approaches,
including anterior and posterior approaches.

[0142] In preferred forms of the invention, a method for implanting a
prosthetic intervertebral disc having shape memory is practiced with the
spinal disc implant delivery devices described herein. As an example, the
method may be practiced with device 800 as depicted in FIGS. 38-44. After
implant 40 is deformed by, for example, manual force into a substantially
straightened, non-relaxed, unfolded, configuration for insertion through
an aperture formed in the annular fibrosis, it is loaded, or otherwise
positioned in cavity 803 of syringe housing 802. Alternatively, as seen
in FIG. 38, implant 40 may be straightened as it is inserted into cavity
803 at proximal end 804 of housing 802. Distal end 809 of plunger 806 may
then be inserted into cavity 803 from proximal end 804 of housing 802.
Device 800, loaded with implant 40, may then be positioned adjacent
aperture 18 in annulus 19 as seen in FIG. 40. Distal end 882 of movable
members 880 are preferably positioned through aperture 18 in annulus 19
and preferably extend into intervertebral disc space 20 surrounded by
annulus 19, as seen in FIG. 40. Force is applied to plunger 806,
preferably at its proximal end 807, to contact end 42 of implant 40 for
translation of the implant towards distal end 812 of delivery tool 800.
The force preferably will allow contact of distal end 809 of plunger 806
with an adjacent end of the implant and may be provided manually, with a
mechanical pressurization device, including a caulk gun, or by other
devices and methods known to the skilled artisan, including the force
generator described in U.S. Pat. No. 5,800,849, as well as other
hydraulic, pneumatic, manual or power-assisted hydraulic force
generators. It is noted that, when utilizing device 700, 700', 700" or
700"', the tip portion of these devices may act as a distractor to
distract the disc space, although a distractor may also be used depending
on the circumstances and preference of the surgeon.

[0143] As implant 40 enters cavity 883 (cavity 883 being seen in FIG. 36)
defined by movable members 880 in their closed configuration, movable
members 880 begin to move radially, or otherwise flex or bend radially,
as seen in FIG. 41. Radial movement of movable members 880 allows the
movable members to contact the surrounding annular tissue and press or
otherwise push the tissue such that the annular defect, or other opening
such as aperture 18, is dilated. This allows implant 40 to exit distal
end 812 of delivery device 800 and enter intervertebral disc space 20 as
seen in FIGS. 41-43, wherein movable members 880 are seen in their open
configuration.

[0144] As mentioned above, implants described herein having arms of
differential length can facilitate implantation and proper positioning of
the implants in the intervertebral disc space. For example, such an
implant having an off-center closure may prevent possible excessive
rolling of the implant during insertion so that the implant will be
positioned such that the length of the implant extends substantially
parallel to the coronal plane of a patient's body.

[0145] It is noted here that distal end 809 of plunger 806 may retain
movable members 880 in their open configuration as end 42 of implant 40
approaches distal end 812 of delivery device 800 prior to completely
exiting the device. After the plunger is translated a sufficient amount
distally to allow implant 40 to exit the device, if necessary, the
plunger is retracted, or translated in a proximal direction to ensure the
deforming members are in their closed configuration as seen in FIG. 44.
Delivery device 800 is then removed. As seen in FIG. 44, implant 40 is
properly positioned in intervertebral disc space 20.

[0146] Referring now to FIGS. 45-48, placement of the spinal implant
delivery devices having tip portions 710, 710', 710" and 710"',
respectively, in an intervertebral disc cavity 20, is shown. As can be
seen in the figures, the distal ends of the tip portions preferably
extend slightly, e.g., about 1 mm to about 10 mm, past the inner face, or
wall, I of annulus fibrosus 19. FIG. 49 is a view along line 49-49 of
FIG. 45 showing placement of tip portion 710.

[0147] The preferred delivery instrument, or device, and methods described
herein are compatible with Medtronic Sofamor Danek's MetRx.TM.
microdiscectomy system and surgical procedures.

[0148] As will be appreciated from the drawings, in some embodiments the
intervertebral disc nucleus pulposus implants comprise an anterior
portion having an anterior height, and a posterior portion having a
posterior height. Additionally, a central portion having a central height
may be described between the anterior portion and the posterior portion.

[0149] In some embodiments any or all of the anterior, posterior, and
central portions may have a uniform height when the implant is not
compressed by an intervertebral load. That is, the height of each or all
of those portions may be substantially the same regardless of where in
the portion the height is being measured. In other embodiments the height
of a portion depends on the specific location being evaluated. (It is
understood that even in such uniform height embodiments, a curvature at
or near the edge of the implant may provide a smaller height at or very
near the edge of the implant.) When the height depends on the location
being evaluated, the relationship between the height of that portion and
the height of any other portion may be described as greater or smaller by
using either average heights or maximum heights in the portions being
evaluated and compared.

[0150] In some preferred embodiments the height of each of the portions is
substantially the same as the height of the other portions. In other
preferred embodiments the heights of the various portions may vary from
portion to portion. For example, the anterior height may be greater than
the posterior height, or the anterior height may be less than the
posterior height. When the implant comprises a central portion, the
central portion may have a height that is greater or less than either or
both of the anterior and posterior portions.

[0151] With reference to the drawings and to the intended orientation of
the implants, FIGS. 50A-D show various views of implant 500, including a
top view (FIG. 50A), a posterior view (FIG. 50B), an anterior view (FIG.
50C), and a lateral view (FIG. 50D). FIGS. 51A-D through 54A-D show
similar views of implants 510 through 540, including top views (FIGS. 51A
through 54A), posterior views (FIGS. 51B through 54B), anterior views
(FIGS. 51C through 54C), and lateral views (FIGS. 51D through 54D).

[0152] As shown in FIGS. 50A-D, some embodiments of the present invention
provide implants in which each of the various sections of the implant has
a substantially uniform height, and in which the heights of the various
sections are all substantially the same. As indicated above, a curvature
at or near the edge of the implant provides a smaller height at or very
near the edge of the implant, but the majority of the implant area has a
substantially uniform height. More particularly, anterior portion 502 has
a substantially uniform height H502 that is substantially the same as the
substantially uniform height H504 of posterior portion 504.

[0153] In contrast, FIGS. 51A-D show an embodiment in which the height of
the anterior portion is substantially uniform, but the height of part of
the posterior portion decreases, i.e., tapers, toward the posterior side
of the implant. More particularly, anterior portion 512 has a
substantially uniform height H512, but posterior portion 514 has a height
that decreases/tapers toward posterior edge 514e. The central portion 513
of the implant is substantially flat. This "posterior sloping" or
"wedge-shaped" or "tapered" embodiment increases the space between the
vertebrae at the anterior portion of the vertebrae, and may be used
advantageously to create or maintain lordosis in the lower lumbar spine.

[0154] FIGS. 52A-D show another embodiment in which the height of the
anterior portion is substantially uniform, but the height of the
posterior portion decreases, i.e., tapers, toward the posterior side of
the implant. In this embodiment the entire posterior portion 524 of the
implant has a height that decreases/tapers toward posterior edge 524e.
Here too, the "posterior sloping" or "wedge-shaped" or "tapered" shape
increases the space between the vertebrae at the anterior portion of the
vertebrae, and may be used advantageously to create or maintain lordosis
in the lower lumbar spine.

[0155] FIGS. 53A-D show an embodiment in which the height of the implant
decreases or tapers from the anterior edge to the posterior edge of the
implant. As shown in the drawings, in this embodiment anterior portion
532 has a height that decreases from anterior edge 532e inward, while
central portion 533 and posterior portion 534 similarly have a height
that decreases toward posterior edge 534e. Like implant 510, implant 530
is a "posterior sloping" or "tapered" embodiment increases the space
between the vertebrae at the anterior portion of the vertebrae, and may
be used advantageously to create or maintain lordosis in the lower lumbar
spine.

[0156] In FIGS. 54A-D, the height of the central portion is substantially
uniform, but the height of the posterior and anterior portions slopes
(decreases) or tapers toward the posterior and anterior edges,
respectively, of the implant. As shown in the drawings, in this
embodiment central portion 543 is substantially flat (i.e., has a uniform
height), while anterior portion 542 slopes downward toward anterior edge
542e, and posterior portion 544 slopes downward toward posterior edge
544e.

[0157] In other, non-illustrated embodiments the height of the central
portion may decrease toward the center of the implant, while the height
of the posterior and anterior portions is substantially uniform. In such
embodiments the central portion of the implant presents a valley in the
implant, with the anterior portion sloping upward toward the anterior
edge, and the posterior portion sloping upward toward the posterior edge.

[0158] It is to be appreciated that in the embodiments having "sloping" or
"tapered" surfaces, it is not necessary for the slopes to be linear or
straight. As used herein, "slope" or "sloping" or "taper" means
transitioning from a greater height to a lesser height (or from a lesser
height to a greater height when going the other way), and the transition
may be linear, or arcuate, or some other shape unless a specific type of
transition is indicated. Thus, unless otherwise indicated, any of the
surfaces of the implant may be flat, or they may be concave or convex or
some other shape. Further, in some preferred embodiments the surface is
uneven or textured, with wavy or undulating surfaces being provided in
some preferred embodiments.

[0159] Further, the amount of slope or taper in the sloped or tapered
embodiments may be selected according to the needs of the patient. For
example, in some embodiments the height of the anterior portion of the
implant is between 5 mm and 15 mm, with the height of the posterior side
of the implant being between 40% and 90% of that height. Most preferably,
the height of the anterior portion of the implant is between 5 mm and 15
mm, with anterior portion heights of between 7 mm and 13 mm being more
preferred and anterior portion heights of between 8 mm and 12 mm being
most preferred. The height of the posterior portion of the implant is
correspondingly preferably between 3 mm and 13 mm, with anterior portion
heights of between 5 mm and 11 mm being preferred for some embodiments
and anterior portion heights of between 6 mm and 10 mm being preferred
for other embodiments.

[0160] The ratio of the maximum anterior height to the minimum posterior
height is generally between 1.0:0.90 and 1.0:0.40, with ratios between
1.0:0.90 and 1.0:0.60 being more preferred. Depending on the medical
condition being treated, ratios between 1.0:0.90 and 1.0:0.70 may be more
preferred for some patients, while ratios of between 1.0:0.70 and
1.0:0.50 may be more preferred for other patients. In embodiments in
which the implant tapers toward the anterior side, the ratios described
above may apply to the ratio of the central height to the anterior
height.

[0161] It is also to be appreciated that the tapering implants do not need
to taper all the way to the posterior (or anterior) side. In some
embodiments the implant tapers part of the way to the side, and then
levels out so that the implant includes a tapered portion and a
substantially flat portion.

[0162] Also as described herein, in some embodiments the surface may be
provided with surface features to reduce or eliminate cracking when the
implant is folded or straightened or compressed, and/or to reduce the
material in the side wall to allow the implant to deform more under load
and to allow a greater range of motion. For example, the implants may
include one or more circumferential grooves to relieve stress and/or
reduce cracking and/or to allow greater deformation and a greater range
of motion when the implant is compressed under an intervertebral load.
When placed under a load, the implant compresses into the circumferential
groove, allowing an increased range of motion. As shown in the drawings,
"circumferential" grooves are preferably arranged on a side surface of
the implant, and may extend around the entire circumference of the
implant.

[0163] FIGS. 55A-F show such circumferential grooves as grooves 556a
through 556c on implant 550. Circumferential grooves such a grooves
556a-c may be used in combination with grooves G shown in FIG. 22N above.
Alternatively, slits or grooves that do not extend all the way around the
implant may be used in addition to, or instead of, circumferential
grooves such as grooves 556a-c.

[0164] In other embodiments the implant is modified to include portions
that are more or less rigid than the predominant implant material. For
example, a softer or harder material may be provided in some portions of
the implant to provide greater or less resistance to compression.
Alternatively, voids may be provided in the implant to achieve stiffness
modification. All of these modifications provide an implant having one or
more areas with a compressive modulus that is different from the
compressive modulus of the predominant portion of the implant. In the
context of this description, a compressive modulus is the characteristic
of the "material" (which may be a void) that describes how the material
compresses or deforms when acted upon by compressive forces such as the
loads typically encountered by intervertebral discs. Thus, the
compressive modulus relates to and characterizes, among other things, the
resistance to compression at various loads, and the type and amount of
deformation of the material when compressed by a load.

[0165] The modifier may be a foam, a gel, a hydrogel, a plastic, or
another material that is softer and/or more pliable and/or more
compressible than the predominant implant material. Alternatively, the
modifier may be a metal, a ceramic, a plastic, or another material that
is harder and/or stiffer and/or less pliable and/or less compressible
than the predominant implant material.

[0166] The modifier may be dispersed throughout the implant when broad
implant modification is desired, or it may be concentrated in one or a
few locations when more localized modification is desired. In some
preferred embodiments the modifier is concentrated in the posterior
portion of the implant so that the posterior portion is more or less
compressible than the remainder of the implant. In other embodiments the
modifier is concentrated in the anterior portion of the implant so that
the anterior portion is more or less compressible than the remainder of
the implant.

[0167] FIGS. 56-58 show modified implants as described above. In FIG. 56
an implant 560 that is modified by including voids 567 in the posterior
and anterior portions of the implant is shown. Similarly, FIGS. 57A-B
show an implant 570 that is modified by filling portions of the implant
with one or more pieces of a softer plastic 577, thereby making some
portions of the implant more compressible. FIG. 58 shows an implant 580
that is modified by filling portions of the implant with a harder
material 587, thereby making portions of the implant less compressible.

[0168] In some embodiments the implant is provided with markers to assist
a surgeon in positioning the implant. For example, radiographic markers
such as metal pins of various sizes and/or shapes (e.g., a round bead, or
a rectangular or cylindrical rod) may be included in the anterior and/or
posterior portions of the implant so that the orientation and/or
positioning of the implant may readily be determined using radiographic
techniques. For the purposes of this description, a radiographic marker
is a marker that can be observed visually or otherwise by one or more of
the radiographic techniques used in the diagnosis and/or treatment of
medical patients. In some preferred embodiments the radiographic marker
may be made of tantalum or tungsten or barium sulfate or combinations of
those or other materials.

[0169] FIGS. 59-60 show radiographic marked implants as described above.
In FIG. 59 an implant 590 having radiographic markers 598 in both the
posterior and anterior portions of the implant is shown. In contrast,
FIG. 60 shows an implant 600 having radiographic markers 608 only in the
posterior portions of the implant. These drawings are provided for
illustrative purposes only; with one or more similar markers being
positionable essentially any place in the implant that is desired.

[0170] In other embodiments the disc nucleus implant may be augmented by
including stem cell material in or around the implant. The stem cell
material may be from undifferentiated cells, or it may be from cells that
have differentiated and have subsequently been returned to their
undifferentiated state. Regardless of whether the cells have begun to
differentiate before selection for use in a disc space, the stem cell
material may comprises cells that have been induced to express at least
one characteristic of human intervertebral disc cells (such as fibroblast
cells, chondrocyte cells, or notochordal cells) before the material is
implanted in a disc. Also, undifferentiated stem cell material and a
material capable of inducing stem cell differentiation may be combined
just prior to, during, or after implantation in a disc space so that the
stem cell material differentiates in the disc space to express at least
one characteristic of human intervertebral disc cells.

[0171] In some embodiments, the stem cell material is provided in
conjunction with a collagen-based material, which may be a collagen-rich
lattice. The collagen-based material may be provided in dehydrated form,
and rehydrated after administration, or it may be provided in a hydrated
form, such as a slurry or gel. Cross-linking agents such as
glutaraldehyde may be included in the collagen-based material to promote
collagen crosslinking.

[0172] In addition, radio-contrast materials may be included in the stem
cell additive to enhance imaging. Performance-enhancing additives such as
analgesics and/or antibiotics may also be included with or without stem
cell material to provide additional benefits. In some preferred
embodiments the stem cell material is provided as a stem cell isolate,
which may be substantially free of non-stem cell material.

[0173] Further embodiments and details of the use of stem cell material in
an intervertebral disc space are described in applicant's copending U.S.
patent application Ser. No. 10/402,723, the entire contents of which are
hereby incorporated into this disclosure by reference.

[0174] In addition, the implants described herein may be augmented by
injecting or otherwise providing collagen-rich material, which may be
collagen-rich natural tissue, into the disc space with the implant and/or
other materials. The collagen-based material may be derived from natural,
collagen-rich tissue, such as intervertebral disc, fascia, ligament,
tendon, demineralized bone matrix, etc. The material may be autogenic,
allogenic, or xenogenic, or it may be of human-recombinant origin. In
alternative embodiments the collagen-based material may be a synthetic,
collagen-based material. Examples of such collagen-rich tissues include
disc annulus, fascia lata, planar fascia, anterior or posterior cruciate
ligaments, patella tendon, hamstring tendons, quadriceps tendons,
Achilles tendons, skins, and other connective tissues.

[0175] The collagen-based material may be injected in a dehydrated form,
and rehydrated after implantation, or it may be injected in a hydrated
form, such as a slurry or gel. The material may be fresh or frozen.
Cross-linking agents such as glutaraldehyde, succinaldehyde,
carbodiimides, diisocyanates, and azide derivatives may be included in
the injected material to promote collagen crosslinking. In addition,
radio-contrast materials may be included to enhance imaging of the
injected material. Similarly, performance-enhancing and/or biologically
active additives such as analgesics and/or antibiotics and/or
anti-inflammatory agents (such as anti-TNF alpha, anti-IL2, anti-IL4,
anti-IL10, anti-IL12, anti-IL18, etc., may be included to provide
additional therapeutic benefits.

[0176] Further embodiments and details of the use of collagen-rich
materials in an intervertebral disc space are described in applicant's
copending U.S. patent application Ser. No. 10/704,167, the entire
contents of which are hereby incorporated into this disclosure by
reference.

[0177] While the invention has been illustrated and described in detail in
the drawings and foregoing description, the same is to be considered as
illustrative and not restrictive in character, it being understood that
only the preferred embodiment has been shown and described and that all
changes and modifications that come within the spirit of the invention
are desired to be protected. In addition, all references cited herein are
indicative of the level of skill in the art and are hereby incorporated
by reference in their entirety.